1975 Zenith Solid State console no color demod

[Mangie]

Hello yall! I got a 1975 Zenith all solid state console set. Model G4547M, Chassis 23GC45. I got the service manual on order. I have basic knowledge and troubleshooting skills on a few vacuum tube sets I own and worked on. This is my first Soild State set. I probably qualify as a noob. Lol Thought I'd see if any pros out there can point me in a direction to start looking. Also if there is any good service tips or things I should do to this set before it goes into semi daily use.

Here is what I've checked out and noticed so far.
First it has a nice good solid black and white picture.
CRT tests really strong and equal on all 3 color guns.
If flip the setup switch on the Croma board, I get a barber poll like colors. Same if I adjust color killer pot. I cleaned up all pot controls.

Looks mostly un touched behind the back cover from what I can tell. However the tuner shield is missing and the ground strap was removed and not reconnected. Not sure if that was from as half attempt at a previous repair or if this was where the previous person tracked the color problem down too and quit at this point.

Thanks much everyone!

[Electronic M]

Barber poleing is the chroma sync oscillator being off frequency. Once you get the service manual there'll be a procedure to adjust it. If the adjustments don't work you could probably swap the color module.

[Mangie]

Originally Posted by Electronic M

Barber poleing is the chroma sync oscillator being off frequency. Once you get the service manual there'll be a procedure to adjust it. If the adjustments don't work you could probably swap the color module.

Well, we can't have that sync being off frequency hehehe. Cool to know the reason behind it. I'll check that out first.

[zeno]

1) set to service, the SW on the board.
2) adj the APC control o bars just slowly go by.
3) SW to normal, adj ACC control per manual.
If the IC's are in sockets get rid of the sockets but IIRC
the sockets were gone by G-line sets.

Watch out for dirty Chromatic switch also.
Or be lazy & just change the 9-86 ( -01 ? ). Still thousands of them around.
Many NOS.

73 Zeno

[Mangie]

Originally Posted by zeno

1) set to service, the SW on the board.
2) adj the APC control o bars just slowly go by.
3) SW to normal, adj ACC control per manual.
If the IC's are in sockets get rid of the sockets but IIRC
the sockets were gone by G-line sets.

Watch out for dirty Chromatic switch also.
Or be lazy & just change the 9-86 ( -01 ? ). Still thousands of them around.
Many NOS.

73 Zeno

Thanks for the alignment tips!

oh! Didnt think of the Chromatic switch. I shall give that a good cleaning as well. Also looks like the IC's are not in sockets and soldered right in.

Took a quick look on the ebay and I didnt see anything Chromatic switch or the board. Is there a good place to find parts for these old Zenith's

[Mangie]

Linked a few pictures of the set for viewing pleasure

https://photos.app.goo.gl/5jSn1FDVwdiY8WyX8

[Mangie]

Well my first Zenith sure is going to be a wild ride. Schematic and manuals showed up today, was going to start troubleshooting on that color problem and do some voltage readings on the chroma board. But my Zenith had another idea. No picture came up today. Checked for HV and got none at the CRT. So guess switch gears to fixing this problem. I probed with my HV probe a few connections at the trippler and the flyback and didnt get anything. Not sure where I should poke next. Also I noticed something interesting on the vertical module, looks like someone tacked on a resistor from ground to a point on the module pin.

https://photos.app.goo.gl/WRuYqAmjUbcUmhyLA

[radiotvnut]

No HV can be several things on these, but when there is no HV and the circuit breaker does not trip, the most common problems are a big 10W or 20W (can't remember) low resistance wirewound resistor that is located on the flat portion of the chassis, on the extreme right-hand side. I've had a few of these sets come to me, where the resistor had opened up at some point, and the service shop simply jumped it with a clip lead (I'm not suggesting that you do that, if the resistor is open).

Another thing that will kill HV is lack of horizontal drive out of the horizontal oscillator/driver module and I've also seen the horizontal driver transformer develop an open winding. IIRC, there is a small electrolytic capacitor from the emitter of the horizontal output transistor to ground and if this cap opens, it can cause the driver module and/or the horizontal output transistor to fail (if the HOT shorts, it will trip the circuit breaker).

Dirty module contacts and cracked solder connections on the module contacts are common. Clean all of the module contacts with contact cleaner and a brush (both on the chassis and on the boards themselves), and re-tension the contacts so they are making a firm connection.

HV triplers are also a very common failure, but when they go, they'll generally short and trip the circuit breaker. I've also seen cases where the tripler will short and take the flyback and HOT with it. Also, I've seen triplers crack and arc to the chassis.

In comparison to later Zenith sets, these CC2 sets are generally easy to troubleshoot, especially with the service manual.

[zeno]

First you will hear about the 4 lead cap. It is NOT one of the
bad ones but can fail. DO NOT fiddle with it or the HV can go up
to 40KV & start to destroy things NO SHANGOING!
Two of the leads complete the HOT E to ground circuit.
Two others the HOT C to flyback circuit.
IIRC it uses the 800-860 kit BUT get the part number first & I can
look it up. Format is 22-####-##
There are a few different ones & you gotta use the right one.

Quick check for H drive on most sets is check the voltage on the C of the
H drive transistor. ( 9-90 module). IIRC apx 75 V normal. If high
or low osc / drive is out. Last thing is Zenith often interlocked the
modules so if one is loose or out the set goes dead.

BTW I have no idea what that wire is about but I dont like it.

73 Zeno
LFOD !

[init4fun]

Originally Posted by zeno

...... NO SHANGOING!....

Thanks for the smile Zeno, that reminds me of "Words that aren't in the dictionary, but should be"

Here's a local one that I'll bet Zeno will know, but not many outside of eastern New England will ;

"Storrowing" , , or, to have been "Storrowed" .....

[Mangie]

Well Fella's, got home from work a bit late, but I had to jump into it. Curiosity been pulling at me all day lol. But I think I am on to something here with yall's help and had to get an update out, even though I haven't finished with all the poking.

First I checked them big resistors in the back bottom right, they both seemed to be close to spec.

Next I pulled and cleaned the boards and connections and tighten down the pins a bit.
didnt see any cracks or bad solder, but I suppose it could be hidden or not well seen.

Tried plugging the set back in, still no HV. However I noticed some smoke coming from the horizontal board. circuit breaker isnt tripping for the record. Found resistor 801 was getting real hot, burning off that deoxit that got on it lol. well that just so happens to be close to the drive transistor Zeno is talking about, think iirc looking at the schematic, that its connected to the drive transistor it or real close. so I got voltage readings on it and the collector is at 103v and half what the schematic says on the emitter. so that is waaaay of the 74 volts.

So what would be next best thing to check if the osc/drive is out? How does one check the horizontal drive transformer to see if there is an issue with that.

Oh I dont like that wire-resistor mod much at all myself. I am hoping it was just a failed resistor on the board and this was someones quick and dirty way of fixing it. I am going to dig into that later once I get things working again and make that right.

[Mangie]

Originally Posted by zeno

First you will hear about the 4 lead cap. It is NOT one of the
bad ones but can fail. DO NOT fiddle with it or the HV can go up
to 40KV & start to destroy things NO SHANGOING!
Two of the leads complete the HOT E to ground circuit.
Two others the HOT C to flyback circuit.
IIRC it uses the 800-860 kit BUT get the part number first & I can
look it up. Format is 22-####-##
There are a few different ones & you gotta use the right one.

Quick check for H drive on most sets is check the voltage on the C of the
H drive transistor. ( 9-90 module). IIRC apx 75 V normal. If high
or low osc / drive is out. Last thing is Zenith often interlocked the
modules so if one is loose or out the set goes dead.

BTW I have no idea what that wire is about but I dont like it.

73 Zeno
LFOD !

You speaking about shango066? hehehe I love his video's
I like radiotvnut videos as well Found that channel because of shango.
anyways,

My capacitor kit is 22-7504-01

Speaking about part numbers. My chroma board is 9-86-01 E
There currently isnt any on ebay, but ebay has 9-86-02 R
is that compatible to use on this set?

[zeno]

For cap use the 800-860 kit. Talon has it listed as in stock.
9-86-01 shows no subs BUT if someone has the old CRSP
module book double check that & the old OEM Zenith dealers.
It may sub up but not down.

Zeno

[Mangie]

Originally Posted by zeno

For cap use the 800-860 kit. Talon has it listed as in stock.
9-86-01 shows no subs BUT if someone has the old CRSP
module book double check that & the old OEM Zenith dealers.
It may sub up but not down.

Zeno

You recon that orange safety cap needs replaced? I just so happen to have the exact same one on hand new in the package that was part of a tube sale not long ago

[zeno]

Originally Posted by init4fun

Thanks for the smile Zeno, that reminds me of "Words that aren't in the dictionary, but should be"

Here's a local one that I'll bet Zeno will know, but not many outside of eastern New England will ;

"Storrowing" , , or, to have been "Storrowed" .....

SHANGO gets me yelling all the time. He does some amazing things but
you cant mess around with that.
OK on unlisted words. I just wish they would change some spellings like
Worcester to Wistah
Chelmsford to Chemsfid etc

Zeno